Dependability evaluation of bus and ring communication topologies for the Delta-4 distributed fault-tolerant architecture

The authors report a study of the dependability of the various communication topologies that can be used to construct a Delta-4 system. Single and dual bus and ring configurations are possible (based on 802.4, 802.5, and FDDI standards); the authors give closed-form expressions for the reliability and availability of each topology when repair is taken into account. It is shown that the dimensioning parameter in the dependability of the communication system is the coverage of the self-checking mechanisms built into the network attachment controllers